Lactation

Question 1

What does mature milk contain?

Answer 1

Energy, lipids, casein, whey, nonprotein nitrogen and lactose

Question 2

What happens during early pregnancy for lactation?

Answer 2

Lobules/alveoli grow during early pregnancy to make more milk-producing cells

Question 3

Where is milk stored?

Answer 3

In alveoli

Question 4

Describe development of lactation

Answer 4

Human alveoli adequately differentiated to produce milk from 16 weeks’ gestation and prolactin is being produced but full lactation does not occur until postpartum period

Question 5

What hormones stop lactation during pregnancy?

Answer 5

Prolactin secreted from 16 weeks’ but breast tissue unresponsive - steroid block (inhibited by oestrogen and progesterone)

Question 6

What hormonal changes occur at the onset of lactation?

Answer 6

1) Withdrawal of oestrogen and progesterone are essential
2) Prolactin also drops but a steady production is maintained (by suckling)
3) Prolactin drops down as soon as progesterone decreases (was building up as wasn’t having effect) but this level of prolactin is sufficient to stimulate milk production

Question 7

What is the role of suckling in lactation?

Answer 7

Suckling ensures prolactin secretion, full lactogenesis and copious milk production

Question 8

What happens if there is no suckling or over-suckling?

Answer 8

• If no suckling small amount of milk produced 3-4 weeks (need to suckle to ‘order food’
• Over-suckling is normal and sign of growth and need for more milk

Question 9

What are the stages of milk development?

Answer 9

1) Milk secretion
2) Colostrum
3) Transitional milk
4) Mature milk

Question 10

What kind of pathway drives milk production?

Answer 10

Neuroendocrine reflex/pathway

Question 11

What is milk production very separate from?

Answer 11

Milk ejection

Question 12

How does suckling stimulate and ensure milk production?

Answer 12

1) Suckling stimulates production of VIP (vasoactive intestinal peptide - protein releasing factor) and reduces dopamine (prolactin inhibitory factor) release
2) Prolactin goes into blood to alveoli and stimulates epithelial cells lining alveoli to produce milk

Question 13

What does the strength an duration of suckling determine?

Answer 13

Strength and duration of suckling determines the amount of prolactin released from the anterior pituitary - this determines the amount of milk made to be available for subsequent feeds

Question 14

When does the milk ejection reflex occur?

Answer 14

When the alveoli is full of milk and ready to feed immediately

Question 15

What type of reflex is the milk ejection reflex?

Answer 15

Neuroendocrine (spinal) reflex

Question 16

What is milk ejection?

Answer 16

When milk is transported from the alveoli to the nipple

Question 17

Describe the process of the milk ejection reflex (MER)

Answer 17

1) Suckling stimulates paraventricular and supraoptic nuclei to produce and release oxytocin from posterior pituitary
2) Circulating levels of oxytocin increase which target myoepithelial cells
3) Oxytocin (smooth muscle contractant) causes contraction of myoepithelial cells surrounding the alveoli full of milk
4) Milk is propelled into ducts and intramammary pressure builds up
5) Milk spurts through the nipple (causes immediate ejection fo milk to nipple to baby)

Question 18

What is special about the milk ejection reflex?

Answer 18

This response can be conditioned e.g. mother responding to baby’s cry by ejecting milk